Box knock-out.



D PLATT- BOX KNOCK-OUT, I k APPLI C ATiO N FILED AUe.1|. um. A j 1,271,215. I j I Patented July 2 anventoz Clare/1106R I Que age? unrrnn STATES PATENT OFFICE.

CLARENCE D. PLATE, 0F BRIDGEPQBT, CONNECTICUT.

- BOX KNOCK-OUT.

sheet metal boxes and the like and aims to provide a simple and practical form of knock-out which may be readily removed to provide an opening for the insertion of an insulating bushing or the like and which also may be utilized even when in place as a bushing for the passage of conductors therethrough. I

In the accomplishment of these ob ects I 'construct the knock-out piece from an integral'portion of the metal wall of the box or other body and form this knock-out piece with an integral'bu'shing ortion forming a d rounded over at its opposite ends to form a smooth bushing. through rectly inserted. This knock-out piece is made removable by substantially severing the section on which the bushing is formed from the surrounding portion of the wall.

In the accompanying drawing I have illustrated the invention embodied in a practical and preferred form wherein Figure 1', is a front or face view of a section of a box wall showing" one of .the knock-outs in position therein.

Fig. 2 is a sectional view taken substantially on the central plane of the knock-out shown in Fig. 1. v

Fig. 3, is a sectional view showinghow the knock-out may be displaced to permit the insertion of a separate insulating bushing.

Figs. 4, 5 and 6 are broken sectional views showing successive steps in the formation I of the knock-out.

In such drawing the numeral 7 "designates the sheet metal wall of a box or other body and 8 designates the knockout member which is formed from the metal of said wall.

As the construction of the knock-out will possibly be best understood by considering the method by which it is formed, reference is directed'to Figs. 4, 5, 6 and 2. in which successive steps of manufacture are illus trated. In the first step illustrated in Fig. 4 a hole 9 is punched in the sheet metal wall. The metal is then drawn up around this hol to form an integral bushing or neck Specification of Letters mat.

which conducting wires may be di-' extension 10, the walls of this bushing portion being thinned out as indicated in this drawing process. The next step according to the present practice is to substantially sever the section carrying this bushing from the surrounding metal. Thus in Fig. 6 the disk 11 of metal surrounding the base portion of the bushing is shown partially punched from the surrounding metal. This punching operation accomplishes practically a complete severance of'the disk from the surrounding material of the wall and when left in this position the diskis held in place substantially by friction only, so that it may be easily displaced when desired.

In drawing up the bushing the mouth or entrance end of the bushing extension is left with a rounded bearing edge 12 and the last step in the process as described consists in providing a roundedbearing edge at the injury can come to the wires as both ends of the bushing are rounded so as to provide rounded bearing edges for the wires.

When therefore the wiring is of such a size as tov pass through the bushing aperture the use of insulatin bushings may be dispensed with and the wiring be simply insert-ed throu h the bushing. In cases however where arger wiring is employed the knock-out piece may be readily displaced from the hole whichit occupies by a light blow with a hammer and a separate bushing of larger size such as that indicated at 14 in Fig. 3 may be inserted in the hole 15 thus left by the integrally formed bushing.

The invention will from the foregoing be seen to possess all the advantages of a simple and inexpensively produced knock-out which may be easily removed when necessary and which may also be left in position to provide a satisfactory bushing for the passage of electrical wiring.

I claim:

1.' In a knock-out construction, a sheetmetal body having a portion of thewall thereof drawn up into an integral tubular bushing and rolled over at theinner end of-such bushing into a rounded bearing edge and the opposite or entrance end of such integral Patented J u1y-2, 1918.

Application filed August 11, 1917.. Serial No. 185,668.

ing edge, whereby to permit the introduction of conducting wires directly through such bushing and said integrally formed bushing being further substantiallysevered from the metal surrounding the base portion of the bushing whereby the bushing as a whole may be knocked out of the wall of which it is formed to provide an opening to receive a separate independent bushing of larger size. 2. In a knock-out construction, av sheet metal body having a hole punched in the Wall thereof and the disk provided by the punching of such hole retained frictionally in place therein, said disk having a portion thereof drawn up and into an integral tubular bushing'provided with rounded bearing edges at its opposite ends, whereby conducting wires may be. passed directly through said integral bushing or the disk the integral bushing may be entirely resaid bushing as a whole to carrying moved from the hole to enablethe insertion of a separate bushing.

3. In a knock-out construction," a sheet metal body having a portion of the wall thereof thinned out and vdrawn up into an integral tubular bushing, said thinned bushing having the inner end thereof rolled over to form a rounded bearing edge and the opposite or entrance end of the bushing hav-' edge, whereby to ening a rounded bearin ucting wires directly able insertion of con in said bushing-and a section of the material surrounding the base portion of the bushing being substantially severed from the wallof which it is formed to thereby enable be knocked out of the wall to permit insertion of aseparate bushng of larger size in the'hole thus prov1 e CLARENCE D. PLATT. 

